UK GAS-Prices ease as domestic supply expected to increase

* Gas system undersupplied by 5 mcm/day

* UKCS supply nominated at 113 mcm/day

July 15 (Reuters) - British prompt gas prices edged lower on Wednesday as nominations showed domestic gas deliveries were to rise later in the day and help reduce tightness in the system.

Prices for within-day delivery were 44.65 pence per therm at 0730 GMT, down 0.30 pence from their last settlement.

Gas for delivery on Thursday was 0.10 pence lower at 44.50 pence per therm.

With supply flows at about 161 million cubic metres (mcm) per day on Wednesday and demand expected to be about 166 mcm, the system was 5 mcm undersupplied, National Grid (LSE: NG.L - news) data showed.

Gas flows from the UK Continental Shelf (UKCS) were at 104 mcm/day, 3 mcm down from the previous day, but nominations showed they would rise to about 113 mcm/day on Wednesday.

"We forecast UKCS flows at around 115 mcm/day for the next two weeks, with a decrease on July 29 due to the start of maintenance at the Britannia field," analysts at Thomson Reuters (Dusseldorf: TOC.DU - news) Point Carbon said.

Temperatures in Britain are predicted to rise up to 27 degrees on Thursday from a maximum 25 degrees on Wednesday, Britain's Met office said.

So far, only one LNG tanker, Al Safliya, is due to arrive in Britain in July, but analysts at Thomson Reuters Point Carbon said another tanker from Qatar, Al Mafyar, may land about July 26-28.

Further out along the curve, gas for August delivery inched up 0.15 pence to 43.40 pence/therm.

Britain is facing its tightest winter power supplies in a decade, mostly due to power plant closures, National Grid said on Wednesday.

On the gas side, supplies are expected to be sufficient to meet demand, which stood at 47.5 billion cubic metres (bcm) last winter. But curbs on production at the Groningen field in the Netherlands and reduced capacity at Britain's largest underground storage at the Rough reservoir were creating some uncertainty, it said.

The storage capacity at Rough is restricted by between one quarter and one third and its operator Centrica (LSE: CNA.L - news) is expected to update the market in October on whether the restriction will be maintained over the winter.

In the Netherlands, gas for Thursday delivery at the TTF hub was steady at 21.10 euros per megawatt hour.

Europe's benchmark carbon price edged up 0.08 euro to 7.82 euros a tonne. (Reporting by Nerijus Adomaitis; editing by David Clarke)